Ashwagandha: what's the evidence?

Summary

Podcast Summary: "What's That Rash?" – Ashwagandha: what's the evidence?
ABC Australia | Aired: July 21, 2026
Host: Norman Swan & Jacinta Boehler

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Episode Overview

This episode of "What's That Rash?" explores ashwagandha (Withania somnifera), a cornerstone herb in Ayurvedic medicine, responding to listener Wayne’s question about its effectiveness in reducing cortisol and mitigating stress. The hosts, Norman Swan and Jacinta Boehler, critically dissect the traditional claims, current scientific evidence, potential benefits, and notable risks of ashwagandha, all while considering cultural context and research gaps.

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Key Discussion Points & Insights

What Is Ashwagandha?

• Origins & Meaning:
  • Norman introduces ashwagandha as an "evergreen shrub cultivated in tropical and subtropical areas of Asia, Africa and Europe." (03:12)
  • Jacinta explains the Sanskrit roots: "'Ashwa means horse and gandha for smell...when we're saying ashwagandha, we're saying effectively wet horse.'" (03:26)
• Ayurvedic Context:
  • Part of the ancient Indian system of medicine, often used as a broad-spectrum "tonic" (04:07).
  • Integrated in ‘rasayana’—herbal or metallic preparations aimed at promoting youth, health, and happiness.

Understanding the Supplement

• Chemical composition varies by plant part (root vs. leaf) and preparation, impacting effectiveness and consistency (05:13).
• Standardization of supplements is a major challenge; reputable products exist, but less reliable ones are common online (05:42).

Risks and Safety Concerns

• Major Risks:
  • Not safe in pregnancy or breastfeeding; risk for those with hormone-sensitive prostate cancer or people on other sedative or anti-clotting medications.
  • Documented cases of liver injury, diarrhea, vomiting, drowsiness, and rare fatal outcomes, especially in those with pre-existing liver disease (06:37–08:01).
• Memorable Quote:
  • Norman: "If something is strong enough to have an effect on the body...it's strong enough to have side effects. There’s just no such thing as an intervention which actually has biological benefits for the body without a biological downside." (07:21)
  • Jacinta: "If it has the power to do good, it has the power to do evil also." (07:49)

Claimed Benefits & The Evidence

1. Stress & Anxiety Reduction

• Listener Question: Wayne asks whether ashwagandha truly reduces cortisol and offsets the consequences of stress (02:03).
• Evidence Review:
  • Mixed evidence, with small, methodologically weak studies, mainly in India. Standardization is often lacking and placebo controls questionable.
  • Some well-conducted studies in Australia and the US do show a "signal" for positive effects on stress, anxiety, depression, and even food cravings (10:28), but the research is short-term and with limited methodological rigor.
• Limitations:
  • Unclear if ashwagandha is better than other interventions, and "most of the studies are short-term without long-term safety." (12:22)
• Notable Caveat:
  • "There's a lot of recommendations around not taking this supplement for more than about 12 weeks at a time because that can increase your risk of the liver side effects." (12:00)

2. Sleep Promotion (Somnifera)

• Evidence for sleep benefits is slightly stronger for people with diagnosed insomnia (13:09).
• Normal sleep restoration and effects after cessation are not well understood.
• Some compounds may have antioxidant or anti-inflammatory effects, potentially relevant to sleep and cognition (13:09–14:29).

3. Cognition and Brain Health

• Scant and low-quality research, with only minor signals that ashwagandha might improve cognitive function, possibly via anti-inflammatory or antioxidant pathways (14:29).

4. Athletic Performance & Testosterone

• Laboratory evidence suggests mild testosterone and DHEA boosts; "it’s possible that you are getting effects on muscle tissue which could improve adaptation to resistance training," but studies are inconclusive (14:39).
• Research lacking in depth and rigor.

5. Anti-Cancer Properties

• In vitro studies suggest promotion of apoptosis (cell death), which is relevant in cancer biology, but this is far from clinical proof (09:03).

Underlying Issues: Research Quality & Cultural Bias

• Pharma & Funding Gaps:
  • High-quality, large-scale research unlikely due to funding issues—no incentives for drug companies to invest in studies on unpatented herbs (15:49).
  • Norman: "It's research that you'll never get because it's so expensive to do..." (15:49)
• Colonial & Cultural Lens:
  • Hosts reflect on Western biases in discounting traditional medicines, acknowledging efforts to apply modern scientific scrutiny to ancient remedies (01:56, 15:21).

Practical Advice & Takeaways

• If trying ashwagandha:
  • Use "small doses in a standardized extract."
  • Buy from reputable, in-person retailers.
  • Inform your GP, especially prior to surgery or if you’re on other medications (16:20).
  • Monitor for side effects, particularly liver-related concerns.
• Be wary of studies and products that do not report side effects—this is a red flag for scientific rigor (17:27).

Looking Ahead

• Norman predicts: "You’ll see the occasional medication emerging out of this space...But I think in 10 years time we've been using traditional medications. People like the idea of traditional medications...and I suspect you're still going to see it being used because people like the idea of it." (18:11)

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Memorable Quotes

• "If it has the power to do good, it has the power to do evil also."
  — Jacinta Boehler (07:49)
• "There’s just no such thing as an intervention which actually has biological benefits for the body without a biological downside."
  — Norman Swan (07:21)
• "If you're going to try Ashwagandha, try it in small doses in a standardized extract...Let your GP know you're on them."
  — Norman Swan (16:01)
• "I think in 10 years time...you're still going to see it being used because people like the idea of it. It feels more natural than modern medicine, personally. Give me the wires, the concrete and the things that go ping every time."
  — Norman Swan (18:11)

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Timestamps for Key Segments

• 01:07 – Introduction to Ayurvedic medicine
• 03:03 – Ashwagandha basics & origins
• 06:37 – Health risks and side effects
• 10:28 – Research on stress, anxiety, and depression
• 12:00 – Limits on duration and safety
• 13:09 – Evidence on sleep
• 14:29 – Cognition and brain health
• 14:39 – Athletic performance and testosterone
• 15:21 – Western biases; research needs
• 16:01 – Practical safety advice
• 18:11 – Future perspectives

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In Summary:
Ashwagandha may have real but modest effects on stress and sleep (primarily in the short term), but comes with risks—especially for the liver and in vulnerable populations. The scientific evidence for its broader claims is inconsistent and generally lacks high methodological quality. The hosts stress the importance of caution, transparency with healthcare providers, and skepticism about products and studies lacking thorough safety reporting. Ashwagandha remains a compelling example of how ancient remedies intersect with modern evidence, scientific limitations, and cultural perceptions.

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Transcript

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[Jacinta Boehler]

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[Norman Swan]

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[Jacinta Boehler]

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[Norman Swan]

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[Norman Swan]

So where do you sit? Tegan with Ayurvedic in a chair. Oh, good. Well, in that case, where do you sit on your chair with Ayurvedic medicine? Have you tried it out?

[Jacinta Boehler]

Well, not sort of intentionally trying out Ayurvedic medicine, but I do love yoga. You know, I've eaten things with turmeric in them. I think it has infused used a lot of our lives in ways that maybe we're not realizing, but I haven't actively sought it out.

[Norman Swan]

So, I mean, we're talking here about ancient Indian practice effectively. The same way as you've got Chinese medicine, which goes back thousands of years, you've got Ayurvedic medicine, which cuts across interventions which include philosophy, religion and beliefs about the way the body works. That's what we're talking about here. But there's lots of interventions around and there are people who do practice ancient Indian medicine in the form of Ayurvedic practice.

[Jacinta Boehler]

It's the sort of thing I think some people might look down their noses at a little bit. And I want to interrogate that a

[Norman Swan]

bit today on what's that Rash, which

[Jacinta Boehler]

is the show where we answer the health questions that everyone is asking. So today's question comes from Wayne, and Wayne is asking a question, as we skillfully foreshadowed, about a particular ingredient in Ayurvedic medicine. So Ashwagandha, Wayne says, I have a question regarding the effectiveness of Ashwagandha in reducing cortisol levels and therefore perhaps some of the adverse consequences of stress. I see from a search or two on the Internet that there is some indication that clinical trials show a reduction. Are those trials meaningful? Is the amount of reduction enough to offset high stress and warrant taking the supplement? Wayne, you are asking excellent questions because we're talking about a traditional medicine. As we said before, we're talking about evidence. And I think today, Norman, we're also going to end up talking about things like imperialism and colonialism, conflicts of interest. It is a very rich seam that Wayne has opened up with his question today.

[Norman Swan]

But it starts with Withania somnifera.

[Jacinta Boehler]

Right. Which is a mouthful. Which is the Latin name for the plant that ashwagandha comes from.

[Norman Swan]

It's an evergreen shrub cultivated in tropical and subtropical areas of Asia, Africa and Europe.

[Jacinta Boehler]

A fact that you just had on the top of your brain and definitely didn't read off a Wikipedia entry.

[Norman Swan]

Tripped off the tongue.

[Jacinta Boehler]

Do you know why it's called ashwagandha?

[Norman Swan]

No, I don't know why it's called

[Jacinta Boehler]

ashwagandh, the Sanskrit name for this plant. But the plant's roots are said to smell like a wet horse. Ashwa means horse and gandha for smell. So that's, that's what we're saying. When we're saying ashwagandha, we're saying effectively wet horse.

[Norman Swan]

Is that a way of testing whether or not you've got genuine ashwagandha?

[Jacinta Boehler]

I think you need to have a wet horse nearby to compare the scent. So that, that is expensive as much as anything else. So, okay, let's talk about this plant, what we know about the plant.

[Norman Swan]

Yeah, it's also called Indian winter cherry or Indian ginseng. And in fact, it's one of the core herbal medications of the Ayurvedic system and has apparently been used for millennia for its wide ranging health benefits.

[Jacinta Boehler]

Yeah, sort of as a tonic, a kind of overall health tonic. And so that's not that uncommon in traditional medicines that you might sort of have something that's like good for you in capital letters. But then the science is really about unpicking what the claims are and how well they're supported by the actions, which is really what we're going to talk about today.

[Norman Swan]

Ye. But in Ayurvedic medicine, there is this mix, if you like, called rasayana, which is described as a herbal or metallic preparation. And they've been advertised for millennia as inducing a youthful state of physical and mental health and expanding happiness, which goes to ween's question.

[Jacinta Boehler]

Yeah. So stress, release, happiness. The Latin name that you said before, Withania somnifera somni in the species name there indicates that it's sometimes used as a sleep aid. It promotes sleep. There's a lot of different health claims here. I'm very curious to sort of pick apart what those claims are and how the science bears them out.

[Norman Swan]

Because of course, if you go look at the Rasayana herbs, there's quite a few herbs in there. It could be a mix and Ashwagandha is just one part of that mix, albeit an important part.

[Jacinta Boehler]

And even then, Ashwagandha is sort of like a catch all for this one plant. Sometimes what you're taking is a root extract, sometimes it's a leaf extract. The chemical composition of the root and leaf differ. So there's a couple of different moving parts here.

[Norman Swan]

There are. Assuming that what you're buying is what is said on the label.

[Jacinta Boehler]

Right. Is this a good time to talk about what we're sort of up against when we're looking at something that's a supplement or approved for use as a supplement versus something that's approved for use as a medicine?

[Norman Swan]

So it's a little less of a problem with Ashwagandha than it is with other supplements. There are forms of Ashwagandha which seem to have verified amounts in them that are more reliable products than just buying them online and hoping for the best. And some of those products have actually been used in clinical trials because standardization is a real problem.

[Jacinta Boehler]

Yeah. This really is a case study in unpicking the powers that be across supplement and drug industries and sort of where research comes from and how quality it is. Top line is that there is some claims that seem to be backed up by evidence that Ashwagandha is good for stress and sleep and performance and those sorts of things. We'll dig into them in a second. I think one thing that would be good to highlight really early on if we're talking about benefits, is to talk about some risks because there are some potential serious health risks from this supplement as well.

[Norman Swan]

So again, whether this is from Ashwagandha itself or from contaminants, it's considered not safe in pregnancy or breastfeeding. It's not considered safe if you've got hormone sensitive prostate cancer because there is some evidence that it influences hormones such as testosterone, that you wouldn't have it at the same time as other sedatives because it may have a sedative effect, it may have an antichlomatic clotting effect. So if you're having surgery, you wouldn't want to necessarily have it. There have been liver problems reported with Ashwagandha. People get diarrhea, vomiting, drowsiness, upper gastrointestinal discomfort. And as we've said many times, if something is strong enough to have an effect on the body, even if it might be a thousand year old herbal medicine, if it's strong enough to have an effect, it's strong enough to have side effects. There's just no such thing as an intervention which actually has biological benefits for the body without a biological downside. Just doesn't happen. And therefore you can't just say, well, I'm having Ashwagandha, it must be safe, it's got all these benefits, it's just like any other drug. It could have a problem and liver injury is one of them.

[Jacinta Boehler]

Yeah. I think there's sometimes a sense that something natural is either good or benign. It's either doing you good or it's not doing anything. But what you're saying is if it has the power to do good, it has the power to do evil also.

[Norman Swan]

Yeah. And there've been rare reports of fatal liver injury. You're needing emergency liver transplantation, particularly in people who've got pre existing liver disease and cirrhosis. And there's a lot of people now in the community with pre existing liver disease because they've got fatty liver disease. So it's not. You can't just say, well, I haven't been drinking, therefore I've not got cirrhosis. Some people do have fatty livers and Ashwagandha could potentially interfere with that. But again, you just simply. It's so hard to tell whether it's Ashwagandha or Ashwagandha with contaminants.

[Jacinta Boehler]

Let's talk about the claims. Wayne kind of summarised some of them in his email. Basically what I've been able to find is there's claims around improved sleep, stress and anxiety reduction, improving cognition, improving athletic performance and boosting testosterone in men. Is there anything there I've missed?

[Norman Swan]

Well, is there much less? When you've got this broad spectrum of effects, it starts to lose believability.

[Jacinta Boehler]

But you just said if something could have an effect somewhere, it could have an effect somewhere else. It's plausible that this could do all of these things.

[Norman Swan]

It is plausible. And because it's a herbal product, it's got lots of different things in it. And as you quite rightly said at the beginning, depending on where they've taken it from which species of plant they've taken it from, it could have a different mix of active compounds in them. So not all would necessarily produce that effect. The other effect that people have noticed when they look at it in the test tube is, is that it promotes a process called apoptosis, cell death, cell death, natural cell death, and some cancers, if not all cancers. And a lot of this work has been done at the Walter and Liza Hall Institute in Melbourne. At least some cancers are a failure of natural cell death. So cells are born, cells live, do their job, and then cells die. And apoptosis is one of the processes that gets rid of cells in that natural cycle. And when ap, the risk is that you get cancer. And in the test tube, Ashwagandha preparations seem to induce apoptosis, which in theory could help if you already have a tumour.

[Jacinta Boehler]

Okay, so some pretty big claims here. Whenever we're thinking about something with anti cancer properties, the hype meter goes all the way up to 11. Let's start with the crux of Wayne's question, which is really about stress and anxiety. What do we know?

[Norman Swan]

Well, what we know from reviews of the evidence. And you've got to be careful with reviews of the evidence because when reviews of the evidence bring together the available studies, but when the available studies lack credibility or lack methodological rigor, you're just adding up errors in your systematic review. A lot of the research has been done in India, as you might imagine. This is not particular to India. There are plenty of lousy randomized controlled trials done all over the world. But a lot of the research into Ashwagandha is not necessarily standardized to preparations. They're small studies, difficult to measure outcomes. The placebo is not necessarily a true placebo, if indeed there's a placebo at all, because the Ashwagandha itself causes side effects and it's possible to recognize when you're taking it versus placebo. So when you look at that methodological rigor, some of these studies really start to fall apart. Nonetheless, there's been West Australian research, US research which have tried to standardize for the preparation of Ashwagandha and seem to find signals of positive effects on stress, anxiety, depression, even food cravings. And again, how can you say that about one thing? Because it's not one thing. It's a melange of different substances which can have varying effects each on their own. Which is why pharmaceutical industry has an interest in Ashwagandha. Is, are one or two of these constituents of Ashwagandha possible drugs for the

[Jacinta Boehler]

future and then one of the things, we didn't say it explicitly before, but there's a lot of recommendations around not taking this supplement for more than about 12 weeks at a time because that can increase your risk of the liver side effects that you mentioned before. So it's not like you kind of go on this as an alternative to going on a long term drug like this is a short term maybe help.

[Norman Swan]

Well, again, you don't get the benefit without the downside. And what people have not shown is whether or not there are most of the studies are short term without long term safety. And you don't know the relapse rate. You don't know head to head whether it's better than having psychotherapy, for example, or better than having an ssri. What's it like head to head with other treatments.

[Jacinta Boehler]

Okay, so I'm getting a bit of a hand wavy outcome with, with the stress and anxiety reduction that perhaps there's a signal there. But it's hard to say what the long term effects are. What about. Okay, we're talking about something species named somnifera. Sleep inducing is another sort of promise of Ashwagandha. What does the science tell us?

[Norman Swan]

Again with all. I'm not going to go over all the caveats that I've just had, but they apply to the sleep research as well. But if you synthesize it, if there is a sleep effect, it seems to be more prominent in people with insomnia rather than just, you know, I have trouble getting off to sleep once every so often. And what we again men don't know about sleep is does it restore normal sleep pattern? What happens when you stop it? There are very effective treatments for insomnia usually based on psychotherapy rather than drugs. And drugs are not recommended over an extended period of time. So it's quite possible it has a somnolent effect. I mean there are other things in the Ashwagandha as well, which it's not entirely obvious why it would have an effect on stress, anxiety and sleep because a lot of the beneficial compounds, the appearing compounds in ash Ashwagandha seem to be having antioxidant effects on the body. So they may be anti inflammatory effects. So they slow down the tissue aging process, the oxidative stress, they may reduce inflammation and so on. And that could happen in the brain too, which is why some people think it might have a benefit on cognitive function. Again, not great research in that area. A little bit of a signal that it might do that. Again because of the mix of compounds in there and some may actually have an effect on brain inflammation, we don't know.

[Jacinta Boehler]

So you mentioned cognition in there. I don't want to get too repetitive. Let's barrel through to one of the ones that doesn't seem to sit well alongside sleep. Improved athletic performance.

[Norman Swan]

Well, I mean, I don't want to bag this completely but again, because of the breadth of effects of the various compounds within Ashwagandha, it's possible that through anti inflammatory effects, it's possible if it does for some reason and there is a little bit of laboratory evidence that it might boost testosterone levels and might boost dhea, which is a precursor of testosterone, it's possible that you are getting effects on muscle tissue which could improve adaptation to resistance training, for example. So it's not out of court that it could have this effect. But again, you need better research to be sure.

[Jacinta Boehler]

It's hard to have a conversation like this without sounding maybe a little bit snobby, like a little bit like. Well, western medicines have been studied in this sort of way and there's sort of like a residual effect that these have been considered to be alternative medicines for a very, very long time. We're starting to get that science coming through. It's still pretty equivocal. As you're saying, Norman, what kind of heft of research would you need to be satisfied that there was a true signal here?

[Norman Swan]

Well, it's research that you'll never get because it's so expensive to do and it's drug companies who fund it. And this is the problem where you have potentially useful products out there but they never get studied. I mean aspirin was a classic example for decades. Some signals that it's really good for after a heart attack to 25 years for that to be nailed because it required public funding of research to prove it. Because no drug company was going to make money out of aspirin. So this is the problem that you've got here. I mean where I would sit just looking at the research for this, what's that rash would be. If you're going to try Ashwagandha, try it in small doses in a standardized extract. We can't tell you what they are. We are not going to. That's where angels fear to tread. But do your research, find that out. And certainly don't buy it on the Internet. Buy it from somebody that you can look in the eye over the counter, can tell you what the provenance is. And the important thing with, with all these complementary medicines because they do have an effect is Let your GP know you're on them. People frightened to tell your GP because they think you're going to get slammed. But good gps will just be grateful to know you're on them because there can be interactions, there can be interactions with drugs to stop your blood clotting and what have you. So it's just really useful to know, especially if you're heading for surgery, so make sure that they go into your notes so that people know you've got them. And watch it carefully because there are side effects.

[Jacinta Boehler]

Because as we said before, liver damage is one of the big kind of top line potential risks here.

[Norman Swan]

And that's the problem with some of these randomised trials, is they don't report on side effects or complications. So if you see a randomised trial which doesn't report on side effects or complications or say there were none, you'd be running for the hills. You wouldn't be relying on that study at all, because it's impossible to have something that's effective without side effects.

[Jacinta Boehler]

And so what we're seeing there, once it's in market, we're sort of starting to see these reports coming out.

[Norman Swan]

Yeah. And as we know, our regulators are not necessarily great at responding to problems that they see in the marketplace.

[Jacinta Boehler]

I know you hate it when I ask you to pull out your crystal ball, Norman, but I'm going to ask you to pull out your crystal ball. If you were looking forward 10 years into the future, what do you imagine we will see coming out of this space?

[Norman Swan]

I think you'll see the odd, the occasional medication emerging out of this space. The pharmaceutical industry puts a lot of money into looking at herbal products to see if they can find something useful out of it. You'd have thought with ashwagandha, since it's so common, if there was something useful in it, they would have found it already. But these things take a while to evolve and emerge onto the market. So it's unclear at the moment what's going to happen, so you could see results. But I think in 10 years time we've been using traditional medications. People like the idea of traditional medications, traditional substances like this, and I suspect you're still going to see it being used because people like the idea of it. It feels more natural than modern medicine, personally. Give me the wires, the concrete and the things that go ping every time.

[Jacinta Boehler]

And I mean, it doesn't all have to be things that go ping. We did actually talk about chronic stress and stress relief last week. If you would like some evidence based natural stress relief techniques go back and listen to last week's what's that rash

[Norman Swan]

with very few side effects, if any.

[Jacinta Boehler]

Well, Wayne, thank you so much for the question. We love getting your questions. You can send them to thatrashbc.net au

[Norman Swan]

and, you know, we'd like to hear from you about what you've learned from what's that rash? How's it helped you, if at all? Have you come a cropper because of what's that rash?

[Jacinta Boehler]

Norman just wants your positive feedback. Norman wants a gold star feedback.

[Norman Swan]

Yeah, just give the negative stuff to Tegan and the positive stuff to me. Have you done some extra research, made any changes? Done an N of 1 trial? We love N of 1 trials. And have you found an alternative to the

[Jacinta Boehler]

Mediterranean diet? Of course you can email us thatrashbc.net

[Norman Swan]

au See you next week.

[Jacinta Boehler]

See you then.